This invention relates to a method for reducing residual formaldehyde in articles of manufacture. In a particular aspect this invention relates to a method of reducing residual formaldehyde in articles manufactured using resins containing terminal methylol groups.
Formaldehyde is a very useful raw material for the manufacture of plastics and resins by condensation with such other raw materials as phenols, urea, furfuryl alcohol, melamines, methylol-containing acrylics and the like. These plastics and resins find a multitude of uses such as in the manufacture of wrinkle-resistant fabrics, non-woven cellulosic articles, particle board, in the preparation of foundry cores and resins, protective coatings, molded products, adhesives, etc.
The importance of dimensional stability, such as wrinkle resistance and durable press properties in textile fabrics and non-woven cellulose products are well established and are of great importance and economic value to the textile industry. The majority of textile articles, both wearing apparel and household articles, available in the marketplace exhibit these properties to some beneficial degree. Although many synthetic fibers inherently possess resiliency and wrinkle resistance, fabrics containing cellulose fibers must be chemically treated to acquire these important properties needed for the modern textile market.
In addition to wrinkle resistance and permanent press properties, it is highly desirable that non-woven cellulosic products display good wet strength characteristics. Yet most paper goods are especially deficient in wet strength unless they are treated.
The principal chemical treatments which produce wrinkle resistance and durable press properties in cellulose-containing textiles and non-woven products are those in which the cellulose molecules are crosslinked, generally by reaction of a di- or poly-functional agent with the cellulose. Many of the agents employed by the textile processing industry to produce durable press properties in cellulosic fabrics are N-methylol adducts formed by reacting nitrogen-containing compounds with formaldehyde. To enhance the reactions between the cellulose and these adducts many compounds or catalysts may be employed.
At present, urea-formaldehyde and urea-glyoxal resins (i.e. the ethylene ureas) are used in large volume. However, glyoxal is a high-cost raw material and it would be advantageous to employ the more economical urea-formaldehyde resin. Other products commonly used to impart wrinkle resistance include cellulose cross-linking agents such as carbamates, triazones, melamines and methylol melamines.
These products, that is, those based on resins having terminal methylol groups, all present another problem, namely, they result in residual free aldehyde, e.g. formaldehyde, on the cloth or other object which is objectionable because it tends to pollute the environment. Similarly, many other industries employing formaldehyde-based resins are faced with occupational health problems involving formaldehyde.